The present invention relates to the field of dentistry, and provides a device and method useful in performing a root canal procedure. Specifically, the invention enables a dentist to find the proper entry point, and entry angle, to access the pulp chamber of a tooth.
Root canal treatment is performed in response to an infection of the pulp of the tooth. The pulp is found in an internal chamber, which is beneath the crown and not visible from the outside. When the pulp becomes damaged, either due to tooth decay, or to dental restoration procedures or trauma, the pulp can become severely inflamed and then infected. This degeneration will often result in a severe toothache and/or a movement of the infection into the bone near the tooth roots. Therefore, when the pulp becomes damaged, it must be removed. This is done through the process of a root canal procedure.
As shown in FIG. 1, the pulp of the tooth fills a contiguous space which includes root canals 2, adjacent to the tooth roots 4, and which also includes a pulp chamber 3, located beneath the crown 1 of the tooth. In a root canal treatment, the pulp must be removed in its entirety, including both the pulp in the pulp chamber, near the crown, as well as the pulp in the root canals.
In a root canal procedure, the tooth is first penetrated so as to expose the coronal portion of the pulp (i.e. the pulp near the crown of the tooth). All of the pulp is then removed, and the empty pulp chamber and root canals are sterilized with various medicaments to insure removal of most bacteria. Finally, the root canals are hermetically filled with a non-toxic filler.
The tooth anatomy shown in FIG. 1, and in many of the other figures, is idealized. In the figure, the crown is well-formed, and the pulp chamber is clearly located directly beneath the crown. But in a real clinical setting, the location of the pulp chamber is often very difficult to ascertain. This difficulty can be due to a variety of reasons:
1) The crown of the tooth may be very heavily restored with old amalgams, composite fillings, or gold inlays.
2) The tooth may have an artificial crown that hides the underlying normal tooth structure. Thus, the normal anatomy of an unrestored tooth, or a lightly restored tooth, which is usually used as guidance for initial penetration, is gone. The artificial crown may be incorrect anatomically, and may give no indication of the true occlusal anatomy of the tooth which is normally used as a guide for initial penetration.
3) The tooth may be tilted or rotated in any direction. When this happens, a crown may be constructed in such a position to correct the tilting discrepancy. This tilting is likely to confuse the dentist with regard to the proper penetration angle for a dental burr.
4) In an elderly patient, the walls of the pulp chamber and root canals narrow, and the pulp chamber may not be easily seen or observed.
5) Almost all dentists currently perform root canal treatments with the patient lying back in a prone position. When the patient is lying back, the angle of the tooth is further distorted, and the correct penetration point and angle of penetration becomes difficult to ascertain.
6) In practice, in many teeth, the pulp chamber may be very small, thready, and calcified, and very different from the idealized concept illustrated in the drawings. The dentist must often penetrate into areas that could be as small as 1 mm in diameter. The margin for error is therefore very, very small.
All of the above conditions, as well other clinical factors, such as inexperience, may lead to difficulty in finding the pulp chamber. An error in locating the pulp chamber can have severe consequences.
First, failure to locate the pulp chamber may prevent the pulp from being removed, and therefore the patient's pain cannot be relieved, and the procedure cannot be performed.
Secondly, if the exact position of the pulp chamber is not known, the penetrating burr may deviate from the proper path needed to enter the pulp chamber. This deviation can cause perforation of the crown, which can lead to loss of the tooth.
Finally, excessive digging around the inside of the tooth can weaken the tooth. It is preferable that the tooth be penetrated not more than once.
Thus, it is imperative that the dentist use every possible aid in locating the pulp chamber. In the prior art, the dentist has been able to rely only on X-rays, on a knowledge of tooth anatomy, and on clinical observations of the patient.
The above methods are ineffectual. The X-ray is only a two-dimensional picture of a three-dimensional object. Knowledge of tooth anatomy is often unhelpful because the structure of the tooth may have dramatically changed due to previous dental work. And clinical observations can be deceptive due to the presence of an artificial crown or other restoration.
A method for locating the pulp chamber has been described in the article entitled “Anatomy of the Pulp-Chamber Floor”, by Paul Krasner et al, Journal of Endodontics, Vol. 30, No. 1 (January 2004). The method uses, as a reference point, the cemento-enamel junction (CEJ), which is the junction of the cementum 5 and the enamel 6 of the tooth, as shown in FIG. 1. The CEJ is essentially the “neck” of the tooth. It is where the enamel of the tooth meets the cementum of the roots. In the cited paper, it is shown that if the perimeter of the tooth is known at the CEJ, then the pulp chamber always lies immediately below the center of this perimeter. That is, the pulp chamber of every tooth is centrally located relative to the external perimeter of the tooth, at the CEJ.
However, the cited article does not provide a practical solution to the problem of locating the pulp chamber. A dentist could probe around the neck of a tooth, but still must form a mental image of its perimeter, and then must translate this knowledge to determine the appropriate point of initial penetration on the occlusal surface of the tooth. This process is very difficult because the gingiva at the neck of the tooth is often swollen and inflamed. Moreover, the process of mentally imaging the structure of the tooth is difficult for many dentists.
In summary, dentists currently have surprisingly little practical information about the true relationship between the observed crown of the tooth, and the root upon which it sits.
The present invention solves the above problem, by providing a simple device and method for locating the pulp chamber of a tooth. The invention provides a simple device which can be easily attached to the tooth, and which can directly show the dentist not only where to enter the tooth, but also the proper angle with which to penetrate the tooth.